docs: def field_stats(self, indices=''):
          """
          Retrieve the field data stats for one or more indices
          (See :ref:'es-guide-reference-api-admin-cluster-nodes-stats')
  
          :keyword indices: an index or a list of indices
          """
          path = self.conn._make_path(indices, (), '_stats','fielddata')
          return self.conn._send_request('GET', path)